Wireless communication systems have evolved to support a higher data rate in order to meet the increasing demand for wireless data traffic. The current wireless communication systems have pursued the development of technology for mainly improving the spectral efficiency in order to increase the data rate, but the increasing demand for wireless data traffic may no longer be met only with the development of technology for improving the spectral efficiency.
In order to solve these problems, the way to use a very wide frequency band may be considered. However, in the frequency band (<5 GHz) used in the current mobile cellular communication system, it is difficult to secure a broader frequency band in reality. Therefore, a broadband frequency could be ensured in a frequency band higher than the current frequency band.
Undesirably, however, as the transmission frequency for wireless communication is higher, the propagation path loss may also be higher. Due to the increase in propagation path loss, the range of radio waves may be shorter, causing a reduction in service coverage. Beamforming technology has been proposed as one of the important technologies for mitigating the propagation path loss and increasing the range.
An analog beamforming scheme, one of the beamforming technologies, is a method in which transmit beamforming used in a transmitter concentrates a signal transmitted from each antenna in a specific direction using a plurality of antennas. To this end, an array antenna may be used, in which a plurality of antenna elements are combined. With the use of the transmit beamforming, the range of radio waves for signals may be increased, and almost no signal may be transmitted in directions other than the direction, contributing to a significant decrease in interference to other users. Similarly, even a receiver may perform receive beamforming using a receive array antenna, and the receive beamforming may also concentrate reception of radio waves in a specific direction to increase the sensitivity of a signal received in the direction, and exclude signals received in directions other than the direction, from the received signal, thereby blocking interference signals.
As the transmission frequency is higher, the wavelength of radio waves is shorter. Thus, if antennas are configured at intervals of, for example, half wavelength, an array antenna may be configured with more antenna elements in the same area. Therefore, the communication system operating in a high-frequency band may easily apply the beamforming technology since the system can obtain higher antenna gain, compared with a system that uses the beamforming technology in a low-frequency band.
In this beamforming technology, in order to obtain higher antenna gain, hybrid beamforming may be used, which is given by combining analog beamforming technology with digital precoding technology that is used to obtain the effect of the high data rate in the existing multi-antenna system. In this embodiment, when one or more analog beams are formed by forming beams through analog beamforming, digital precoding may be applied, which is similar to that applied in the baseband in the existing multi-antenna system, so high-reliability signals may be received or high system capacity may be expected. Using the hybrid beamforming may ensure higher performance compared to using only one of analog beamforming and digital precoding, but may cause an increase in implementation complexity.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.